Cannot get camera / lamp aligned after importing DXF file
The problem is your dxf imported objects are by far too large, look how they compare to the blender grid!



If you select all them and scale them by 0.01 they almost fit again in the blender grid... 



like this



now you can add a plane, a sun lamp and a camera and use them correctly



edit: expanding the answer to follow comments request.

I guess opening a new specific question would be better, but: dimensions are relative to the scene units and scale. 

Try this: select a sample mesh (eg: a door panel) go into edit mode, select only a vertical front door edge (it should be around 2 meters). Now in the properties panel (N key) under "mesh display", enable "edge info: length". 

if units are "none" what length does the edge show? 



and what if units are "metric"? 



that door is too high...

You can adjust to the right measure either 


scaling the whole mesh accordingly (try scaling 0.01, and apply scaling) 
scaling the scene metric units by the same amount (both will make your model sized more like the blender grid)


eg: method 2



I hope this help more...